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At least 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Assessment of the grindability of robocast silicon carbide

The demand for high-performance lightweight optics has driven interest in silicon carbide (SiC) due to its exceptional thermal stability, hardness, and strength-to-weight ratio. This study investigates the potential of robocasting, an additive manufacturing process, as a viable method for producing lightweighted SiC components for optical applications. Four samples with varied starting powder phases (α and β) and sintering conditions were fabricated and evaluated. Post-sintering surface and form were assessed using coherence scanning interferometry (CSI) and coordinate measuring machine (CMM) techniques. A three-stage grinding process was applied to each sample, with surface roughness assessed at each stage. Results demonstrate that samples with predominantly α-phase SiC and smaller particle sizes achieved superior surface finish, particularly sample D2-α-2135 °C, which displayed the lowest post-grinding Sq value of 0.178 µm. The analysis also indicated no significant print-through effect from the lightweighting structure, or print artifacts, at this stage of grinding. However, β-phase samples showed poorer grindability, increased surface roughness, and pitting. These findings suggest that phase composition and particle size are critical for achieving the desired surface quality in robocast SiC optics. Future work will incorporate additional samples and finer grinding wheels to refine surface quality further, supporting the development of SiC for high-precision optical applications.

Barrett, Taylor [ORNL]↗
DOE OSTI2014

Atom chip apparatus for experiments with ultracold rubidium and potassium gases

We present a dual chamber atom chip apparatus for generating ultracold {sup 87}Rb and {sup 39}K atomic gases. The apparatus produces quasi-pure Bose-Einstein condensates of 10{sup 4} {sup 87}Rb atoms in an atom chip trap that features a dimple and good optical access. We have also demonstrated production of ultracold {sup 39}K and subsequent loading into the chip trap. We describe the details of the dual chamber vacuum system, the cooling lasers, the magnetic trap, the multicoil magnetic transport system, the atom chip, and two optical dipole traps. Due in part to the use of light-induced atom desorption, the laser cooling chamber features a sufficiently good vacuum to also support optical dipole trap-based experiments. The apparatus is well suited for studies of atom-surface forces, quantum pumping and transport experiments, atom interferometry, novel chip-based traps, and studies of one-dimensional many-body systems.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2015

High-accuracy Aspheric X-ray Mirror Metrology Using Software Configurable Optical Test System/deflectometry

The Software Configurable Optical Test System (SCOTS) uses deflectometry to measure surface slopes of general optical shapes without the need for additional null optics. Careful alignment of test geometry and calibration of inherent system error improve the accuracy of SCOTS to a level where it competes with interferometry. We report a SCOTS surface measurement of an off-axis superpolished elliptical x-ray mirror that achieves <1 nm<1 nm root-mean-square accuracy for the surface measurement with low-order term included.

42 ENGINEERING↗
NASA NTRS2006

The Space Elevator and Its Promise for Next Generation Exploration

Bryan E. Laubscher received his Ph.D. in physics in 1994 from the University of New Mexico with a concentration in astrophysics. He is currently on entrepreneurial leave from Los Alamos National Laboratory where he is a project leader and he has worked in various capacities for 16 years. His past projects include LANL's portion of the Sloan Digital Sky Survey, Magdalena Ridge Observatory and a project developing concepts and technologies for space situational awareness. Over the years Bryan has participated in research in astronomy, lidar, non-linear optics, space mission design, space-borne instrumentation design and construction, spacecraft design, novel electromagnetic detection concepts and technologies, detector/receiver system development, spectrometer development, interferometry and participated in many field experiments. Bryan led space elevator development at LANL until going on entrepreneurial leave in 2006. On entrepreneurial leave, Bryan is starting a company to build the strongest materials ever created. These materials are based upon carbon nanotubes, the strongest structures known in nature and the first material identified with sufficient strength-to-weight properties to build a space elevator.

Laubscher, Bryan E.↗
DOE OSTI2024

X-ray Irradiance Distribution for an Interferometer with a Curved Biprism Array

The development of interferometry-based X-ray phase contrast imaging systems that provide highly resolved X-rays with spatially-modulated intensity is enabling the full potential of X-ray optics to image phase, attenuation, and small angle scatter properties of soft tissue. In this work we present analytical formulations of a new hardware concept for X-ray phase contrast imaging wherein the phase grating is replaced with an array of Fresnel biprisms. We derive expressions for the irradiance distribution pattern of a biprism interferometer composed of a curved biprism array with multiple biprisms and multiple point sources. These expressions are used to plot fringe patterns for X-ray design parameters, including 1) size, number, and period of X-ray point sources; 2) biprism parameters of material composition, angle, number, and period; and 3) biprism array to X-ray source and detector distances. Analytical results show that the biprism interferometer provides a longitudinally-nonperiodic pattern of spatially modulated intensity different from the Talbot longitudinally-periodic pattern common in grating interferometry. The curvature of the biprism array brings a sharper longitudinal fringe pattern. Experiments are being performed to verify the analytical calculations for a biprism plastic material of SU-8 using a synchrotron source. X-ray biprism material has widely varied indexes of refraction relative to wavelength and thus the separation of the virtual sources and resulting interference fringe period also varies with X-ray wavelength. Our aim is to develop biprism interferometry imaging systems with excellent polychromatic performance that produce high-contrast fringes with spatially incoherent X-ray illumination. Biprism interferometry will potentially provide higher fringe visibility with better image quality to that of diffraction grating interferometry.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
NASA NTRS1989

The Next Generation Space Telescope

In Space Science in the Twenty-First Century, the Space Science Board of the National Research Council identified high-resolution-interferometry and high-throughput instruments as the imperative new initiatives for NASA in astronomy for the two decades spanning 1995 to 2015. In the optical range, the study recommended an 8 to 16-meter space telescope, destined to be the successor of the Hubble Space Telescope (HST), and to complement the ground-based 8 to 10-meter-class telescopes presently under construction. It might seem too early to start planning for a successor to HST. In fact, we are late. The lead time for such major missions is typically 25 years, and HST has been in the making even longer with its inception dating back to the early 1960s. The maturity of space technology and a more substantial technological base may lead to a shorter time scale for the development of the Next Generation Space Telescope (NGST). Optimistically, one could therefore anticipate that NGST be flown as early as 2010. On the other hand, the planned lifetime of HST is 15 years. So, even under the best circumstances, there will be a five year gap between the end of HST and the start of NGST. The purpose of this first workshop dedicated to NGST was to survey its scientific potential and technical challenges. The three-day meeting brought together 130 astronomers and engineers from government, industry and universities. Participants explored the technologies needed for building and operating the observatory, reviewed the current status and future prospects for astronomical instrumentation, and discussed the launch and space support capabilities likely to be available in the next decade. To focus discussion, the invited speakers were asked to base their presentations on two nominal concepts, a 10-meter telescope in space in high earth orbit, and a 16-meter telescope on the moon. The workshop closed with a panel discussion focused mainly on the scientific case, siting, and the programmatic approach needed to bring NGST into being. The essential points of this panel discussion have been incorporated into a series of recommendations that represent the conclusions of the workshop. Speakers were asked to provide manuscripts of their presentation. Those received were reproduced here with only minor editorial changes. The few missing papers have been replaced by the presentation viewgraphs. The discussion that follows each speaker's paper was derived from the question and answer sheets, or if unavailable, from the tapes of the meeting. In the latter case, the editors have made every effort to faithfully represent the discussion.

Bely, Pierre-Yves↗
NASA NTRS2000

Semiconductor Laser Linewidth Measurements for Space Interferometry Applications

Narrow linewidth (<100KHz) semiconductor lasers are expected to be a key technology in NASA's stellar interferometry missions to search for planets around nearby stars. Long coherence length lasers are needed for precise (20 pm to 5 mn) measurements of the optical path difference. This work discusses results using the self-heterodyne delay technique to measure 1.3 micrometer InP based DFB lasers. We will also address practical issues concerning detection and elimination of back reflections, choice of fiber length and resolution, and measurement of laser 1/f and current supply noise.

Dougherty, D. J.↗
NASA NTRS2001

Mid-Infrared Interferometry: Science and Technology

Interferometry in the mid-infrared atmospheric window (9-12 microns) is extremely challenging because of the high background due to emission from warm telescope optics and the atmosphere itself. During the past twelve years this challenge has been met by the U.C. Berkeley Infrared Spatial Interferometer (ISI), a heterodyne stellar interferometer comprised of two 1.65 m aperture telescopes mounted in custom semi-trailers. Carbon-dioxide laser local oscillators and LN2 cooled HgCdTe photodiodes are used to down-convert radiation at approx. 30 THz into an approximately 5 GHz (DSB) IF band. The maximum baseline at present is 65 m giving a nominal resolution of 16 milliarcsecs. A third telescope is being integrated with the other two and within the next year will operate as an imaging interferometer providing data with three simultaneous baselines and a closure phase, and baselines up to about 75 m.

Danchi, William C.↗
NASA NTRS2016

NASA's Preparations for ESA's L3 Gravitational Wave Mission

Telescope Subsystem - Jeff Livas (GSFC): Demonstrate pathlength stability, straylight and manufacturability. Phase Measurement System - Bill Klipstein (JPL): Key measurement functions demonstrated. Incorporate full flight functionality. Laser Subsystem - Jordan Camp (GSFC): ECL master oscillator, phase noise of fiber power amplifier, demonstrate end-to-end performance in integrated system, lifetime. Micronewton Thrusters - John Ziemer (JPL): Propellant storage and distribution, system robustness, manufacturing yield, lifetime. Arm-locking Demonstration - Kirk McKenzie (JPL): Studying a demonstration of laser frequency stabilization with GRACE Follow-On. Torsion Pendulum - John Conklin (UF): Develop U.S. capability with GRS and torsion pendulum test bed. Multi-Axis Heterodyne Interferometry - Ira Thorpe (GSFC): Investigate test mass/optical bench interface. UV LEDs - John Conklin+ (UF): Flight qualify UV LEDs to replace mercury lamps in discharging system. Optical Bench - Guido Mueller (UF): Investigate alternate designs and fabrication processes to ease manufacturability. LISA researchers at JPL are leading the Laser Ranging Interferometer instrument on the GRACE Follow-On mission.

Midterm Assessment↗
NASA NTRS1992

Study of optical techniques for the Ames unitary wind tunnels. Part 4: Model deformation

A survey of systems capable of model deformation measurements was conducted. The survey included stereo-cameras, scanners, and digitizers. Moire, holographic, and heterodyne interferometry techniques were also looked at. Stereo-cameras with passive or active targets are currently being deployed for model deformation measurements at NASA Ames and LaRC, Boeing, and ONERA. Scanners and digitizers are widely used in robotics, motion analysis, medicine, etc., and some of the scanner and digitizers can meet the model deformation requirements. Commercial stereo-cameras, scanners, and digitizers are being improved in accuracy, reliability, and ease of operation. A number of new systems are coming onto the market.

Lee, George↗
DOE OSTI2025

Dispersion Leverage Coronagraph: a nulling coronagraph for use on primary objective grating telescopes

Here, we present the Dispersion Leverage Coronagraph (DLC), a variation of the Achromatic Interfero Coronagraph (AIC) that is designed for optical systems featuring large, dispersive primary objective gratings. DLC was originally designed for the Diffractive Interfero Coronagraph Exoplanet Resolver (DICER), a notional 20 m class infrared space telescope utilizing the enhanced one-dimensional angular resolution of large diffraction gratings to discover and characterize near-Earth exoplanets. Here we develop the theoretical foundation for DLC, and apply it to DICER as an example use case. We derive important properties of the DLC system, including focal plane transmission maps, stellar leakage, residual optical path difference tolerance, and pointing error/jitter considerations. Ultimately, we found that DLC effectively nulls an on-axis target across the entire spectrum in the focal plane, allowing for 2D/λ diffraction-limited imaging. It requires asymmetrical fine-guidance tolerances on pointing error/jitter. We work through a benchmark DICER design, explaining the need for a second disperser to reduce background from Zodiacal light, and showing that it could plausibly find and characterize ∼4 nearby, habitable exoplanets around Sun-like stars in a 7-year mission; about 30% of the habitable exoplanets within 8 pc were found in our simulation. The DLC may be useful for any application requiring extremely high-resolution, close companion spectroscopy.

AIC↗
NASA NTRS1994

Infrared astronomy from the Moon

The purpose of this paper is to exhibit the advantages and limitations to infrared astronomical observations form the moon. The most obvious apparent advantage is the lack of a lunar atmosphere; radiation arriving from the universe is neither extinguished nor refracted as it approaches the lunar surface. However, the Earth's atmosphere's protection against cosmic rays is also lost, and infrared detectors are highly sensitive to irradiation by energetic particles. A second apparent advantage is the relative ease with which beams from an array of telescopes can be interferometrically combined; again the vacuum environment with constant refractive index of unity throughout, permits combination without phase delay across the entire spectral range. But thermal radiation from optical components and stray radiation from the lunar environment, just outside the light path, tend to lessen that advantage, except in narrow-spectral-band spatial interferometry, in which only the radiation in individual spectral lines is mapped, and broad-band thermal emission can be effectively filtered out. On the Moon's night side, and in polar craters on the Moon, radiative cooling should permit the attainment of high sensitivity with large telescopes. Just as the proposed Edison spacecraft primary mirror is expected to reach temperatures around 40 K, so also large lunar primary mirrors might be expected to reach temperatures in that range, making the zodiacal glow the main source of noise at wavelengths shortward of 25 micrometers. The slow rota tion of the Moon, and the lack of vibrations from natural sources such as winds, should provide advantages in guiding on specific astronomical sources. To learn as much as possible about the difficulties of remote observations in a hostile environment, Antarctic observatories should be used as test beds for the rigors of lunar observations. The strenuous requirements for successful astronomical observations from the South Pole are similar to those expected to be encountered in observations conducted from the Moon.

Harwit, Martin↗
NASA NTRS2012

Frequency References for Gravitational Wave Missions

The mitigation of laser frequency noise is an important aspect of interferometry for LISA-like missions. One portion of the baseline mitigation strategy in LISA is active stabilization utilizing opto-mechanical frequency references. The LISA optical bench is an attractive place to implement such frequency references due to its environmental stability and its access to primary and redundant laser systems. We have made an initial investigation of frequency references constructed using the techniques developed for the LISA and LISA Pathfinder optical benches. Both a Mach-Zehnder interferometer and triangular Fabry-Perot cavity have been successfully bonded to a Zerodur baseplate using the hydroxide bonding method. We will describe the construction of the bench along with preliminary stability results.

Preston, Alix↗
DOE OSTI2024

Ultrafast temporal phase-resolved nonlinear optical spectroscopy in the molecular frame

In an ultrafast nonlinear optical interaction, the electric field of the emitted nonlinear signal provides direct access to the induced nonlinear transient polarization or transient currents and thus carries signatures of ultrafast dynamics in a medium. Measurement of the electric field of such signals offers sensitive observables to track ultrafast electron dynamics in various systems. In this work, we resolve the real-time phase of the electric field of a femtosecond third-order nonlinear optical signal in the molecular frame. The electric field emitted from impulsively pre-aligned gas-phase molecules at room temperature, in a degenerate four-wave mixing scheme, is measured using a spectral interferometry technique. The nonlinear signal is measured around a rotational revival to extract its molecular-frame angle dependence from pump-probe time-delay scans. By comparing these measurements for two linear molecules, carbon dioxide and nitrogen, we show that the measured second-order phase parameter (temporal chirp) of the signal is sensitive to the valence electronic symmetry of the molecules, whereas the amplitude of the signal does not show such sensitivity. We compare measurements to theoretical calculations of the chirp observable in the molecular frame. This work is an important step towards using electric field measurements in nonlinear optical spectroscopy to study ultrafast dynamics of electronically excited molecules in the molecular frame.

47 OTHER INSTRUMENTATION↗
NASA NTRS2010

LISA Technology Development and Risk Reduction at NASA

The Laser Interferometer Space Antenna (LISA) is a joint ESA-NASA project to design, build and operate a space-based gravitational wave detector based on a laser interferometer. LISA relies on several technologies that are either new to spaceflight or must perform at levels not previously demonstrated in a spaceflight environment. The ESA-led LISA Pathfinder mission is the main effort to demonstrate LISA technology. NASA also supports complementary ground-based technology development and risk reduction activities. This presentation will report the status of NASA work on micronewton thrusters, the telescope, the optical pointing subsystem and mission formulation. More details on some of these topics will be given in posters. Other talks and posters will describe NASA-supported work on the laser subsystem, the phasemeter, and aspects of the interferometry. Two flight-qualified clusters of four colloid micronewton thrusters, each capable of thrust Levels between 5 and 30 microNewton with a resolution less than 0.l microNewton and a thrust noise less than 0.1 microNewton/vHz (0.001 to 4 Hz), have been integrated onto the LISA Pathfinder spacecraft. The complementary ground-based development focuses on lifetime demonstration. Laboratory verification of failure models and accelerated life tests are just getting started. LISA needs a 40 cm diameter, afocal telescope for beam expansion/reduction that maintains an optical pathlength stability of approximately 1 pm/vHz in an extremely stable thermal environment. A mechanical prototype of a silicon carbide primary-secondary structure has been fabricated for stability testing. Two optical assemblies must point at different distant spacecraft with nanoradian accuracy over approximately 1 degree annual variation in the angle between the distant spacecraft. A candidate piezo-inchworm actuator is being tested in a suitable testbed. In addition to technology development, NASA has carried out several studies in support of the mission formulation. The results of systems engineering work on flight software, avionics and reliability will be summarized.

Stebbins, Robin T.↗
DOE OSTI2018

Plasma and radiation detection via fiber interferometry

Photonic Doppler velocimetry tracks motion during high-speed, single-event experiments using telecommunication fiber components. The same technology can be applied in situations where there is no actual motion, but rather a change in the optical path length. Migration of plasma into vacuum alters the refractive index near a fiber probe, while intense radiation modifies the refractive index of the fiber itself. Lastly, these changes can diagnose extreme environments in a flexible, time-resolved manner.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1989

Angular navigation on short baselines using phase delay interferometry

Results are presented for two recent short baseline experiments, with baseline lengths of 6 and 253 km, showing delay residuals of 10 ps or less for angularly close sources. On the 6-km baseline, a fiber-optic link was used to distribute a common frequency reference, enabling coherent operation of the two stations. The observed delay residuals correspond to a differential angular accuracy of about 10 nrad on the 253-km baseline. Future plans are discussed, including the development of a realtime correlation capability on a 22-km baseline at Goldstone, CA.

Edwards, Charles D.↗